dougal-software/etc/db/upgrades/upgrade42-v0.6.4-notify-exclude-columns.sql

-- Add procedure to decimate old nav data
--
-- New schema version: 0.6.4
--
-- ATTENTION:
--
-- ENSURE YOU HAVE BACKED UP THE DATABASE BEFORE RUNNING THIS SCRIPT.
--
--
-- NOTE: This upgrade affects the public schema only.
-- NOTE: Each application starts a transaction, which must be committed
-- or rolled back.
--
-- This update modifies notify() to accept, as optional arguments, the
-- names of columns that are to be *excluded* from the notification.
-- It is intended for tables with large columns which are however of
-- no particular interest in a notification.
--
-- To apply, run as the dougal user:
--
-- psql <<EOF
-- \i $THIS_FILE
-- COMMIT;
-- EOF
--
-- NOTE: It can be applied multiple times without ill effect.
--

BEGIN;

CREATE OR REPLACE PROCEDURE pg_temp.show_notice (notice text) AS $$
BEGIN
	RAISE NOTICE '%', notice;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE PROCEDURE pg_temp.upgrade_database () AS $outer$
BEGIN

	RAISE NOTICE 'Updating schema %', 'public';
	SET search_path TO public;

	-- BEGIN

	CREATE OR REPLACE FUNCTION public.notify()
		RETURNS trigger
		LANGUAGE 'plpgsql'
		COST 100
		VOLATILE NOT LEAKPROOF
	AS $BODY$
		DECLARE
		channel text := TG_ARGV[0];
		pid text;
		payload text;
		notification text;
		payload_id integer;
		old_json jsonb;
		new_json jsonb;
		excluded_col text;
		i integer;
		BEGIN

		-- Fetch pid
		SELECT projects.pid INTO pid FROM projects WHERE schema = TG_TABLE_SCHEMA;

		-- Build old and new as jsonb, excluding specified columns if provided
		IF OLD IS NOT NULL THEN
			old_json := row_to_json(OLD)::jsonb;
			FOR i IN 1 .. TG_NARGS - 1 LOOP
				excluded_col := TG_ARGV[i];
				old_json := old_json - excluded_col;
			END LOOP;
		ELSE
			old_json := NULL;
		END IF;

		IF NEW IS NOT NULL THEN
			new_json := row_to_json(NEW)::jsonb;
			FOR i IN 1 .. TG_NARGS - 1 LOOP
				excluded_col := TG_ARGV[i];
				new_json := new_json - excluded_col;
			END LOOP;
		ELSE
			new_json := NULL;
		END IF;

		-- Build payload
		payload := json_build_object(
			'tstamp', CURRENT_TIMESTAMP,
			'operation', TG_OP,
			'schema', TG_TABLE_SCHEMA,
			'table', TG_TABLE_NAME,
			'old', old_json,
			'new', new_json,
			'pid', pid
		)::text;

		-- Handle large payloads
		IF octet_length(payload) < 1000 THEN
			PERFORM pg_notify(channel, payload);
		ELSE
			-- Store large payload and notify with ID (as before)
			INSERT INTO notify_payloads (payload) VALUES (payload) RETURNING id INTO payload_id;

			notification := json_build_object(
				'tstamp', CURRENT_TIMESTAMP,
				'operation', TG_OP,
				'schema', TG_TABLE_SCHEMA,
				'table', TG_TABLE_NAME,
				'pid', pid,
				'payload_id', payload_id
			)::text;

			PERFORM pg_notify(channel, notification);
			RAISE INFO 'Payload over limit';
		END IF;
		RETURN NULL;
		END;
	$BODY$;

	ALTER FUNCTION public.notify()
		OWNER TO postgres;

	-- END

END;
$outer$ LANGUAGE plpgsql;

CREATE OR REPLACE PROCEDURE pg_temp.upgrade () AS $outer$
DECLARE
	row RECORD;
	current_db_version TEXT;
BEGIN

	SELECT value->>'db_schema' INTO current_db_version FROM public.info WHERE key = 'version';

	IF current_db_version >= '0.6.4' THEN
		RAISE EXCEPTION
			USING MESSAGE='Patch already applied';
	END IF;

	IF current_db_version != '0.6.3' THEN
		RAISE EXCEPTION
			USING MESSAGE='Invalid database version: ' || current_db_version,
				HINT='Ensure all previous patches have been applied.';
	END IF;

	CALL pg_temp.upgrade_database();
END;
$outer$ LANGUAGE plpgsql;

CALL pg_temp.upgrade();

CALL pg_temp.show_notice('Cleaning up');
DROP PROCEDURE pg_temp.upgrade_database ();
DROP PROCEDURE pg_temp.upgrade ();

CALL pg_temp.show_notice('Updating db_schema version');
INSERT INTO public.info VALUES ('version', '{"db_schema": "0.6.4"}')
ON CONFLICT (key) DO UPDATE
	SET value = public.info.value || '{"db_schema": "0.6.4"}' WHERE public.info.key = 'version';


CALL pg_temp.show_notice('All done. You may now run "COMMIT;" to persist the changes');
DROP PROCEDURE pg_temp.show_notice (notice text);

--
--NOTE Run `COMMIT;` now if all went well
--